Semiconductor manufacturing has long required exacting processes to achieve reproducible results. Clean room techniques have been developed and rigorously enforced because any source of contamination may quickly destroy a manufacturing run. However, not all sources of contamination can be prevented from the application of clean room techniques. Indeed, some manufacturing processes are inherently contaminating. For those processes, new procedures and techniques must be developed to reduce or eliminate harmful contaminants in sale and effective manners.
For example, chemical mechanical polishing or planarization (CMP) is one technique used in semiconductor fabrication for planarizing a top surface of an in-process semiconductor wafer or other substrate. CMP processes utilize abrasive and corrosive chemical slurries (commonly a colloid) in conjunction with a polishing pad and retaining ring, typically of a greater diameter than the wafer. The pad and wafer are pressed together by a dynamic polishing head and held in place by a plastic retaining ring. The dynamic polishing head is rotated with different axes of rotation (i.e., not concentric). This process removes material and tends to even out any irregular topography, making the water more or less flat or planar. A CMP step may be necessary, in some devices, to set up a wafer for the formation of additional circuit elements. CMP is considered a “dirty” process because of the introduction of slurry particles to the manufacturing environment. To combat contamination, chemical cleaning processes have teen developed which attempt to clear a substrate of all slurry particles before additional processing takes place.
However, in some examples utilizing CMP processes, slurry particles may resist chemical cleaning (i.e., remain on the surface of the substrate) and may, therefore, adversely affect further processing of substrates. Such slurry particles, which often comprise silica particles, may themselves be hydrophilic. When a surface of the substrate is hydrophobic, and therefore has a high wetting angle, hydrophilic slurry particles may be inaccessible to cleaning solutions, and may, therefore, remain adhered to the substrate after a post-CMP cleaning step. In addition, adhered slurry may provide nucleation sites for complexes formed from post-cleaning process chemistries. In other examples, where slurry particles are characteristically hydrophobic, attachment to a surface may render a device surface less reactive with desired aqueous chemistries. As may be appreciated, particulate contamination may have many undesirable effects. As such, methods for removing residual particles from a substrate are presented herein.